Geological And Geochemical Characteristics And Genetic Research Of Pb-Zn-Ag Deposit In Wulanbaiqi Mining Area Inner Mongolia

Located in XilinHaote-Xilinguole Pb-Zn-Ag metallogenic belts,which is in the southern-middle parts of the DaxinganLing Mountains,the Wulanbaiqi Pb-Zn-Ag deposit is a Medium-scale deposit.In terms of geotectonic position,it locates in the transition zones between the North China plate and the Siberia plate,and it’s close to the North China plate.Regional Erenhot-Hegenshan NEE deep faults lie at the NW side of this region.Through the research on the geological and geochemical characteristics of the Wulanbaiqi Pb-Zn-Ag deposits,main achievements are obtained as follows:（1）The orebodies as stratiform and stratoid,mainly occurred in the lower Cretaceous（K₁by）Baiyingaolao Formation rhyolitic crystal tuff with breccia and debris,meanwhile,part of the orebodies occurred in the Upper Permian（P₃l）politic siltstone.Ore minerals mainly include sphalerite,galena,chalcopyrite,pyrite,Freibergite,Pyrargyrite,Acanthite.While the gangue minerals mainly consist of eldspars,sericite,chlorite,calcite,quartz,arsenopyrite and rutile.The wall alterations mainly represent as sericitization,chloritization,silication,carbonicacidation,pyritization,gypsification,beresitization,pyrrhotitezation and so on.（2）The geochemistry study shows that the volcanic rocks in this mining area enriched in light REE with obvious Eu abnormality.The similar REE patterns indicates that the ore minerals have a same source region with the wall rocks,and the wall rocks may provide parts of Metallogenetic materials for the former.The S and Pb isotope of the ore minerals indicates that the metallogenetic materials characterized with deep seated magma source which contaminated with the wall rock.（3）The ore-host rock,Baiyingaolao Formation volcanic rocks,with the U-Pb age of 127Ma,belongs to Early Cretaceous.Combined with the previous research,concluded that the mineralization happened at Early Cretaceous.（4）According to the geochemistry study of fluid inclusion,the ore-forming fluids have the characteristics of low-middle temperature,low salinity and low density.Connecting with the previous results,the inferrence that the ore-forming fluids mainly came from magma was made,and mixed with a large amount of atmospheric precipitation in the later stage.（5）Combined with the geologic characteristics,closely associated with volcanic-subvolcanic activity during Early Cretaceous,controlled by the faulted structure,the Wulanbaiqi Pb-Zn-Ag deposit belongs to hydrothermal vein type with medium-low temperature.